Apparatus and method for automatically compensating for lateral runout

ABSTRACT

An apparatus and method for automatically compensating for the lateral runout between an on-car lathe apparatus and a vehicle hub axis including one or more stop discs that rotate with the drive shaft of the lathe and that can be selectively stopped from rotating with the shaft by a stop mechanism. In response to such stopping, one or more adjustment discs are caused to rotate in order to adjust the relative position of the axis of the lathe with respect to the axis of the disc brake assembly. In this manner, the system compensates for and corrects lateral runout that exists between two concentrically attached rotating shafts.

BACKGROUND OF THE INVENTION

1. This invention relates to an improved on-car brake lathe apparatus.More specifically, this invention relates to an apparatus and method forautomatically compensating for the lateral runout of a lathe apparatuswith respect to a vehicle hub. The invention further includes a novelrunout measurement and control system that describes the runout of adisc brake assembly and directs a corrective signal to an automatedcontrol system for adjustment in order to effectively compensate oflateral runout. The novel runout apparatus and method may also beadvantageously utilized in other practical applications in order toalign two concentrically attached rotating shafts.

2. A brake system is one of the primary safety features in every roadvehicle. The ability to quickly decelerate and bring a vehicle to acontrolled stop is always critical to the safety of the vehicleoccupants and those in the immediate vicinity. In this, a vehiclebraking system is designed and manufactured to exacting specificationsand rigorous inspection.

3. One of the main components of a brake system are the disc brakeassemblies typically mounted on the front wheels of most passengervehicles. Generally, the disc brake assemblies include a caliper(cooperating with a brake hydraulic system), brake pads, a hub, and arotor. The caliper supports and positions a pair of brake pads onopposing sides of a brake rotor. In a hubless brake rotor (i.e. when therotor and hub are separate components), the rotor is secured to thevehicle hub, via a rotor hat, with a series of bolts for rotation withthe hub about a vehicle spindle axis. When a vehicle driver depresses abrake pedal thereby activating the hydraulic system, the brake pads areforced together and toward the rotor to grip the friction surfaces ofthe rotor.

4. Disc brake assemblies must be maintained to manufacturersspecifications throughout the life of the vehicle in order to assureoptimum performance and maximum safety. However, several problems haveplagued the automotive industry since the inception of disc brakes.

5. A significant problem in brake systems is usually referred to as“lateral runout.” Generally, lateral runout is the side-to-side movementof the friction surfaces of the rotor as it rotates with the vehicle hubabout a spindle axis. Referring to FIG. 1, for example, there is shown arotor having friction surfaces on its lateral sides. A rotor is mountedon a vehicle hub for rotation about the horizontal spindle axis X. In anoptimum rotor configuration, the rotor is mounted to rotate in a plane Ythat is precisely perpendicular to the spindle axis X. Generally, goodbraking performance is dependant upon the rotor friction surfaces beingperpendicular to the spindle's axis of rotation X and parallel to oneanother (“parallelism”). In the optimum configuration, the opposingbrake pads will contact the friction surfaces of the rotor at perfect 90degree angles and will exert equal pressure on the rotor as it rotates.More typically, however, the disc brake assembly will produce at least adegree of lateral runout that deviates from the ideal configuration. Forexample, a rotor will often rotate in a canted plane Y′ and about anaxis X′ which is a few thousandths of an inch out of axial alignmentwith the spindle (shown in exaggerated fashion in FIG. 1). In this rotorconfiguration, the brake pads, which are perpendicular to the spindleaxis X, will not contact the friction surfaces of the rotor along aconstant pressure plane.

6. The lateral runout of a rotor is the lateral distance that the rotordeviates from the ideal plane of rotation Y during a rotation cycle ofthe rotor. A certain amount of lateral runout is inherently present inthe hub and rotor assembly. This lateral runout often results fromdefects in individual components. For example, rotor friction surfacerunout results when the rotor friction surfaces are not perpendicular tothe rotor's own axis of rotation, rotor hat runout results when the hatconnection contains deviations that produce an off center mount, andstacked runout results when the runouts of the components are added or“stacked” with each other. An excessive amount of lateral runout in acomponent or in the assembly (i.e. stacked runout) will generally resultin brake noise, pedal pulsation, and a significant reduction in overallbrake system efficiency. Moreover, brake pad wear is uneven andaccelerated with the presence of lateral runout. Typically,manufacturers specify a maximum lateral runout for the frictionsurfaces, rotor hat, and hub that is acceptable for safe and reliableoperation.

7. After extended use, a brake rotor must be resurfaced in order tobring the brake assembly within manufacturers specifications. Thisresurfacing is typically accomplished through a grinding or cuttingoperation. Several prior art brake lathes have been used to resurfacebrake rotors. These prior art lathes can be categorized into threegeneral classes: (1) bench mounted lathes; (2) on-car caliper-mountedlathes; and (3) on-car hub mounted lathes. As discussed below, theon-car hub mounted lathes have proven to be the most reliable andaccurate rotor refinishing lathes in the industry.

8. Bench mounted lathes, for example, that disclosed in U.S. Pat. No.3,540,165 to Lanham, are inefficient and do not have rotor matchingcapabilities. In order to resurface a rotor on a bench mounted lathe,the operator is first required to completely remove the rotor from thehub assembly. The operator then mounts the rotor on the bench latheusing a series of cones or adapters. After the cutting operation, theoperator remounts the rotor on the vehicle spindle. Even if the rotor ismounted to the lathe in a perfectly centered and runout free manner,runout between the rotor and hub is not accounted for in the bench latheresurfacing operation. In addition, bench lathes are susceptible to bentshafts which introduce runout into a machined rotor. This runout is thencarried back to the brake assembly where it may be added with hub runoutto produced a stacked runout effect.

9. Similarly, caliper-mounted lathes, for example, that disclosed inU.S. Pat. No. 4,388,846 to Kopecko et al., have had limited success incompensating for lateral runout, but require time consuming manualoperations. During a rotor refinishing procedure, the brake caliper mustfirst be removed in order to expose the rotor and hub. Once removed, thecaliper mounting bracket is freed and can be used to mount an on-carcaliper-mount lathe. The caliper-mount lathes are wholly unacceptablefor many reasons including the lack of a “rigid loop” connection betweenthe driving motor and cutting tool and the inability to assure aperpendicular relationship between the cutting tools and the rotor.Moreover, the caliper-mount lathes do not have any reliable means formeasuring and correcting lateral runout. Typically and in much the samemanner as described below with reference to the hub mounted lathes, adial indicator is utilized in determining the total amount of lateralrunout in the disc assembly. This measurement technique is problematicin terms of time, accuracy and ability of automechanics to comfortablyuse the equipment.

10. On-car hub mounted lathes, for example, that disclosed in U.S. Pat.No. 4,226,146 to Ekman, assigned to the assignee of the instantapplication, and incorporated by reference into the disclosure herein,have proven to be the most accurate and efficient means for resurfacingthe rotor.

11. Referring now to FIG. 2, there is shown an Ekman type on-car discbrake lathe 10 for mounting to the hub of a vehicle 14. The lathe 10includes a body 16, driving motor 18, adapter 20, and cutting assembly22. The lathe is also provided with a stand and anti-rotation post (notshown), either of which can be used to counter the rotation of the latheduring a resurfacing operation. After the brake caliper is removed, theadapter 20 is secured to the hub of the vehicle 14 by using the wheellug nuts. The lathe body 16 is then mounted to the adapter 20.

12. At this point in the prior art procedure, the operator mustdetermine the total amount of lateral runout and make an appropriateadjustment. Specifically, the operator first mounts a dial indicator 26to the cutting head 22 using a knob 28. The dial indicator 26 ispositioned to contact the vehicle 14 at one of its distal ends as shownin FIG. 2. Once the gauge 26 is properly positioned, the operator isrequired to take the following steps in order to measure and compensatefor lateral runout:

13. (1) The operator mates the lathe to the rotor using the adapter andprocedure outlined above.

14. (2) The operator activates the lathe motor 18 which causes theadapter 20, and thereby the brake assembly hub and rotor, to rotate. Thetotal lateral runout of the assembly will be reflected by correspondinglateral movement in the lathe body.

15. (3) The lateral movement of the lathe body is then quantified byusing the gauge 26. Specifically, the operator observes the dialindicator to determine the high and low deflection points and thecorresponding location of these points on the lathe.

16. (4) Upon identifying the highest deflection of the dial indicator,the operator “bumps” the motor and stops the rotation at the point ofthe identified highest deflection.

17. (5) The operator then makes an adjustment to compensate for runoutof the assembly. This is accomplished by careful turning of theadjustment screws 24. Specifically, there are four adjustment screws andthe correct screw(s) must be turned depending on the location of thehigh point. The affect of turning the screws is to adjust theorientation of the lathe body with respect to the adapter 20 (andtherefore the rotor and hub) to mechanically compensate for the runoutof the assembly. The operator adjusts the screws until the highestdeflection point is reduced by half as determined by reference to thedial indicator 26.

18. (6) The operator activates the lathe motor 18 and observes the dialindicator 26 to again identify the highest deflection of the dial. Ifthe maximum lateral movement of the lathe body, as measured by theneedle deflection, is acceptable (i.e. typically less than {fraction(3/1000)}) then mechanical compensation is complete and the latheturning operation can commence. Otherwise, further measurement andadjustment will be necessary by repeating steps (1) to (6).

19. The cutting operation is then performed by adjusting the tool holder22 and cutting tools 23, and setting the proper cutting depth.

20. Although the hub mounted on-car brake lathe was a considerableadvance in the disc brake lathe industry, its structure andcorresponding procedure for compensating for lateral runout of the discbrake assembly has practical limitations.

21. First, as readily apparent, upon observation of steps (1)-(6) above,the Ekman procedure requires a significant amount of time to determineand adjust for lateral runout of the brake assembly. Although thespecific amount of time necessary will vary based upon operatorexperience, the procedure time for even the most trained and experienceis significant and can substantially increase the cost associated withrotor refinishing to the vehicle owner and the shop. Second, the priorart system and procedure requires the shop owner and technicians toundergo extensive education and operator training in order to assurethat proper mechanical compensation for lateral runout is accomplished.Moreover, the Ekman system is operator specific. That is, the accuracyand success of measurement and adjustment of lateral runout will varyfrom operator to operator.

22. In general, the prior art systems and procedures are problematicwith respect to accuracy in the measuring and adjusting of lateralrunout. The prior art systems require an operator to locate a highreading for lateral runout by viewing the gauge 26; often, the operatoris required to “bump” the motor to relocate the high point once it hasbeen identified. Moreover, even if the operator correctly locates and/orrelocates the high point of lateral runout, human errors are oftenintroduced during the adjustment process. For example, selecting thecorrect screw or screws 24 and applying the precise amount of torquenecessary for adjustment is often difficult and imprecise.

23. The difficulties and limitations suggested in the preceding are notintended to be exhaustive, but rather are among many which demonstratethat although significant attention has been devoted to disc brakelathes, such systems will admit to worthwhile improvement.

OBJECTS AND BRIEF SUMMARY OF THE INVENTION

24. It is therefore a general object of the invention to provide a novelon-car disc brake lathe system which will obviate or minimizedifficulties of the type previously described.

25. It is another general object of the invention to provide a novelrunout measurement and control system for an on-car disc brake lathethat accurately detects and quantifies the runout of a lathe apparatuswith respect to a vehicle hub assembly.

26. It is yet another general object of the invention to provide a novelautomated alignment apparatus for an on-car disc brake lathe thatadjusts the axial alignment of the lathe in accordance with informationproduced by a runout sensing and control system.

27. It is a specific object of the invention to provide a novel runoutmeasurement and control system for an on-car disc brake lathe thatdirects a corrective signal to an automated control system foradjustment.

28. It is a specific object of the invention to provide a novel on-cardisc brake lathe apparatus which eliminates the need for manualadjustment by an operator in order to compensate for lateral runout.

29. It is another specific object of the invention to provide a novelon-car disc brake lathe apparatus system which will accurately andconsistently measure and adjust for runout.

30. It is still another specific object of the invention to provide anovel on-car disc brake lathe apparatus which will significantly reducethe time required for a complete brake disc lathing operation.

31. It is still yet another specific object of the invention to providea runout measurement and control system for an on-car disc brake lathehaving a processing unit for accurate and reliable data evaluation.

32. It is another specific object of the invention to provide a runoutmeasurement and control system for an on-car disc brake lathe thatadvises an operator or directs an electrically controlled system toperform an axial alignment of the lathe and vehicle hub.

33. It is still another specific object of the invention to provide anautomated alignment device for an on-car disc brake lathe thataccurately adjusts the relative angle between the vehicle hub's axis ofrotation and the lathe's drive shaft.

34. It is yet another specific object of the invention to provide anautomated alignment apparatus for an on-car disc brake lathe that, whenused with a suitable control system, will reduce the total lateralrunout of the lathe with respect to the vehicle hub assembly to withinacceptable manufacturing specifications.

35. It is further specific object of the invention to provide anautomated alignment apparatus for an on-car disc brake lathe that issimple, accurate, capable of computer control, and low in cost.

36. It is another specific object of the invention to provide a runoutmeasurement and control system for an on-car disc brake lathe thatsenses rotational accelerations while rejecting linear accelerations inany of the three dimensional axes.

37. It is another specific object of the invention to provide a runoutmeasurement and control system for an on-car disc brake lathe thatsenses rotational that it is a one piece mechanism mounted securely tothe lathe and not subject to operator error during setup.

SUMMARY OF THE INVENTION

38. The automatic alignment apparatus for an on-car disc brake lathe ofthe present invention which is intended to accomplish at least theforegoing objects includes a brake lathe having an automatic alignmentcoupling that operates in response to a corrective signal to adjust thealignment of the lathe with respect to the vehicle in order tomechanically compensate for lateral runout. The automatic alignmentmechanism includes one or more stop discs that rotate with the driveshaft of the lathe and that can be selectively stopped from rotatingwith the shaft by a stop mechanism. In response to such stopping, one ormore adjustment discs are caused to rotate in order to adjust therelative position of the axis of the lathe with respect to the axis ofthe disc brake assembly. In this manner, the system compensates for andcorrects lateral runout that exists between two concentrically attachedrotating shafts.

DRAWINGS

39. Other objects and advantages of the present invention will becomeapparent from the following detailed description of the invention, takenin conjunction with the accompanying drawings, wherein:

40.FIG. 1 is a graphical representation of a lateral runout phenomenon.

41.FIG. 2 is a plan view showing an on-car disc brake lathe anddepicting a prior art procedure for measuring, and compensating forlateral runout of a disc brake assembly.

42.FIG. 3 is a perspective view showing an on-car disc brake lathemounted on the hub of a vehicle in preparation for a disc resurfacingoperation in accordance with the present invention.

43.FIG. 4 is a partially sectional schematic view of a disc brake lathewith an automatic alignment apparatus of the first preferred embodimentof the present invention mounted on the hub of a vehicle.

44.FIGS. 5a and 5 b are cross-sectional and front views, respectively,of the automatic alignment apparatus of the first preferred embodimentof the present invention.

45.FIG. 6 is a cross-sectional view of the adjustment disc assemblies ofthe automatic alignment apparatus of the first preferred embodiment ofthe present invention.

46.FIGS. 7a and 7 b are front cross-sectional views of one of theadjustment disc assemblies of the automatic alignment apparatus of thefirst preferred embodiment of the present invention.

47.FIGS. 8 and 9 are cross-sectional views of the adjustment discassemblies of the automatic alignment apparatus of the first preferredembodiment of the present invention.

48.FIGS. 10a and 10 b are cross-sectional and side views, respectively,of the automatic alignment apparatus of the second preferred embodimentof the present invention.

49.FIG. 10c is a front and cross-sectional views of an adjustment discof the automatic alignment apparatus of the second preferred embodimentof the present invention.

50.FIG. 10d is a front and cross-sectional views of a slant disc of theautomatic alignment apparatus of a pivot ring of the second preferredembodiment of the present invention.

51.FIGS. 11a and 11 b are schematic representations of the compensationvector and compensation alignment angle of the automatic alignmentapparatus of the second preferred embodiment of the present invention.

52.FIG. 12 is a cross-sectional view of the automatic alignmentapparatus of the third preferred embodiment of the present invention.

53.FIGS. 13a and 13 b are front views of the input and output adaptorassemblies and a front view of the drive arm assembly, respectively, ofthe automatic alignment apparatus of the third preferred embodiment ofthe present invention.

54.FIG. 14 is a front view of the starwheel stop mechanism of the of theautomatic alignment apparatus of the third preferred embodiment of thepresent invention.

55.FIGS. 15a-g is a timing diagram of the starwheel stop operation ofthe automatic alignment apparatus of the third preferred embodiment ofthe present invention.

56.FIG. 16 is a flow diagram of the automatic alignment operationutilizing the automatic alignment apparatus of the third preferredembodiment of the present invention.

57.FIG. 17 is a schematic view of the rotational runout phenomenonoccurring during a cutting operation of the on-car disc brake lathemounted on the hub of a vehicle.

58.FIG. 18 is a schematic view of the linear runout phenomenon occurringduring a cutting operation of the on-car disc brake lathe mounted on thehub of a vehicle.

59.FIGS. 19a and 19 b are front and cross-sectional views, respectively,of a rotary piezo-electric accelerometer of the runout measurement andcontrol system of the of the present invention.

60.FIG. 20 is a front view of a rotary magnetic hall effect transducerof the runout measurement and control system of the of the presentinvention.

61.FIGS. 21 and 21a are front and side views of a rotary infraredgenerator accelerometer of the runout measurement and control system ofthe of the present invention.

62.FIG. 22 is a front view of a rotary tuned coil oscillatoraccelerometer of the runout measurement and control system of the of thepresent invention.

63.FIG. 23 is a circuit diagram of the control system of the runoutmeasurement and control system of the of the present invention.

DETAILED DESCRIPTION

64. Context of the Invention

65. Referring now to FIG. 3, there is shown a perspective view of anon-car disc brake lathe 30 of the present invention mounted to a hub 44of a vehicle 14 brake assembly. The disc brake lathe 30 includes a motor32, body 34, cutting head 36 with cutting tools 38, and adapter 40. Thevehicle disc brake assembly includes a rotor 42 operably attached to ahub 44. Typically, the attachment of the rotor 42 to the hub is througha rotor hat (not shown) formed in the rotor 42 (i.e. a “hubless” rotor).However, an integral rotor and hub is occasionally utilized incommercial vehicles. The adapter 40 is mounted to the hub 42 of thevehicle utilizing the lug nuts 46.

66. Apparatus and Method for Automatic Runout Compensation

67. The novel on-car disc brake lathe with automatic alignment andcompensation mechanism of the subject invention is now described withreference to FIGS. 4 through 9. Referring to FIG. 4, there is shown alathe 48 having an automatic alignment mechanism 50, lathe housing orbody 52, hub adaptor 54, and drawbar assembly 56. The drawbar assemblyincludes a drawbar 58 that extends through the body 52 and alignmentmechanism 50 and is operably connected to the adaptor 54 by a threadedconnected (as shown) or the like. A calibrate knob 60 is tightenedduring the automated alignment sequence of the lathe and after alignmentis complete, a run knob 62 is tightened for the cutting operation.Spring 64 is a belleville washer that provides a loading force on bar 58which in turn runs through the components of the lathe.

68. Referring to FIG. 5a there is shown a cross-sectional view of theauto alignment coupling 50 of the preferred embodiment. An input adaptor66 is operably attached to a rotating drive shaft of the lathe machine(shown in phantom in FIG. 4). Shaft 68 is attached to the input adaptor66 such that the adaptor 66 mounting face is perpendicular to the shaft68 axis so that shaft 68 runs true with the lathe machine axis.

69. Two slant or adjustment disc assemblies 86 and 88 are provided to beinterposed between the input adaptor 66 and an alignment drive disc 70which is attached to the shaft 68 and caused to rotate with it by a key72 and set screw 74. A pivot plate 76 is operably attached to an outputadaptor 78 and mounted to the shaft 68 by spherical bearing 80 so thatthe pivot plate 76 can pivot in relation to shaft 68 while beingconstrained from radial movement.

70. A pin 82, inserted into pivot plate 76, fits into a slot 84 at theperiphery of the drive disc 70 and causes the pivot plate 76 to berotationally coupled to the shaft 68 and input the adaptor 66. As such,when the input adaptor 66 is mounted on the lathe machine's drive shaftand the output adaptor 78 is mounted on the automobile brake discadaptor 54, the lathe machine output rotation will cause the automobilebrake disc adaptor to rotate, in turn causing the brake disc to rotate.

71. The slant or adjustment disc assemblies 86 and 88, which are mirrorsof each other, are placed between the input adaptor 66 and the outputadaptor 78 as shown. The axial force produced by the axially mounteddrawbar 58, that mounts the output adaptor 78 to the automobile brakedisc hub, causes the output adaptor 78 to be forced against slant discassembly 88 and to assume an angle to the shaft 68 that depends upon therelative rotational positions of the slant disc 90 and 92.

72. Referring to FIG. 6, adjustment disc assemblies 90 and 92 are shownin parallel and in positions of maximum angular runout. Control of therelative position of the slant discs 90 and 92 is accomplished while thelathe machine output shaft is driving the automobile brake disc hub.Specifically, by stopping the rotation of stop disc 94 or 96, itsassociated slant disc is caused to rotate in relation to the other slantdisc, thus producing a change in angle of the output of the adjustmentdisc assemblies 86 and 88, causing the angle of the output adaptor 78 tochange in response. This causes a change in the angular alignment of thelathe machine axis and the automobile brake disc axis.

73. As shown in FIGS. 5a and 5 b, the stop discs 94 and 96 areselectively stopped by powering a respective electromagnetic catch 98and 100. The catches are controlled by an microprocessor system thatoperates in conjunction with a runout measurement and control mechanismdescribed in more detail below. The lathe machine output shaft rotatesat a speed that is too fast (for example, 123.14 RPM) to allow stop andrelease of a stop disc and associated slant disc for adjustment. Assuch, the rotation speed of the adjustment components is slowed by usinga gear train contained in each of the slant disc assemblies. The geartrain will extend the time permitted for adjustments in a given ½revolution of the shaft 68 (i.e. the time it takes stop pin 114 to stopthe relative rotation of the slant discs in ½ revolution for maximumangular runout adjustment). For example, the time will extend at 123.14RPM shaft rotation from 0.243 seconds for ½ revolution of the shaft 68to 3.297 seconds thereby permitting easy and complete adjustment of theslant disc assemblies 86 and 88.

74. Referring to FIGS. 6 and 7a, the preferred gearing mechanismcomprises a gear 102 containing 88 teeth, and gear 102 is coupled withkey 104 to rotate with shaft 68. Gear 106 contains 38 teeth and ismounted on a pivot 108 formed on stop disc 94. Thus, when stop disc 94is stopped by the electromagnetic catch 98, gear 106 rotates at a muchfaster rate than shaft 68. For example, if shaft 68 rotates at 123.14RPM, gear 105 rotates at 285.166 RPM. A gear 110, also mounted on pivot108, is provided with 36 teeth and is pinned to gear 106 to rotatetherewith. Gear 110 is coupled to a gear 112 that is provided with, forexample, 90 teeth. As such, gear 112 rotates at 114.06 RPM, or 0.926 Xthe rotational speed of shaft 11, rotating backwards in relation toshaft 68 and slant disc 92. Because slant disc 90 is pinned to gear 112,it also moves backwards in relation to shaft 68 thereby adjusting therelative position of the slant discs 90 and 92. The gear arrangement andstop discs of the present invention permits the adjustment of the slantdisc assemblies, and therefore, the alignment of the lathe drive axisand the hub axis, without the need for a separate motor or power source.It is to be understood that the identified gear ratios and rotationspeeds are practical examples and are not intended to limit the scope ofthe invention hereof. When the stop disc 94 is released, it and slantdisc 90, in its new position, again rotates at the rate of the shaft 68.

75. A stop pin 114 secured to slant disc 92 stops the relative rotationof the slant discs at ½ revolution, with stop disc 94 being parallelwith stop disc 96 at one extreme to maximum angular runout at the otherextreme. Specifically, by stopping the rotation of both stop discs 94and 96, adjustment disc 90 and 92 remain fixed in relation to eachother. Stopping the rotation of stop disc 94 alone until stop pin 114couples to slant disc 90 causes stop disc 96, and thus output adaptor78, to assume the maximum angular runout position.

76. Referring to FIG. 8, the adjustment disc assemblies 86 and 88 andassociated adjustment discs 90 and 92 are rotated in relation to eachother so that the “slant” or wedge on respective interfaces complementeach other and the input surface of the assembly is parallel with theoutput surface. This is accomplished by stopping the stop disc 94 untilthe pin 114 couples with the slant disc 90. Thus the output adaptor 78“runs true” to the input rotation axis. The angle of the interface ofthe two slant discs has been exaggerated in the figures for clarity. Theangle could be of a dimension that depends on the application of thelathe, but could be in the order of 0.323 degrees. It is noted thatbecause the input adaptor 66 is solidly mounted to the shaft 68 and itsface is perpendicular to the axis of rotation, the adaptor 66 serves asa positioning reference to the slant disc assembly 86. Referring to FIG.9, the slant disc assemblies 86 and 88 with the discs are rotated inrelation to each other by stopping the stop disc 96 until the pin 114couples to the slant disc 90. In this position, the slant angle on thetwo slant discs add to each other causing the output surface of theassembly and the output adaptor 78 to display maximum angular runoutwith the input rotation axis.

77. With the novel alignment adjustment system of the present invention,the runout caused by a misalignment between the vehicle's hub axis andthe axis of the lathe can be corrected without the time consuming andinaccurate manual methods of the prior art. With the novel system,additional adjustment motors are not necessary and accurate andautomated realignment is possible when the novel alignment system isoperated in conjunction with a measurement and control system of thetype described below.

78. A second preferred embodiment incorporates the fundamental featuresof those disclosed with respect to the first embodiment, but permitsadjustment with only one slant disc and the output pivots in oneselectable axis only when driven by the slant disc. In the firstpreferred embodiment, the compensation vector (explained in more detailwith reference to FIGS. 11a and 11 b) necessary to adjust the angle ofthe output adaptor 78 could potentially require adjustment of two slantdiscs. The fixed pivoting axis of the second preferred embodimenteliminates this problem, requiring only one adjustment, potentiallyreducing the time required for shaft alignment.

79. Referring to FIG. 10a, there is shown a cross-sectional view of theautomatic alignment coupling or mechanism 120 that occupies the sameposition of the mechanism 50 of the first embodiment shown in FIG. 4.Input adaptor 122 attaches to the rotating shaft of the lathe machine.Shaft 124 is attached to the input adaptor 122 such that the adaptor 122mounting face is perpendicular to the shaft 124 so that shaft 124 runstrue with the lathe machine axis. A second shaft 126 is placed over theshaft 124 and the rotated position of the second shaft 126 relative toshaft 124 is controlled by the stop disc assembly 128. The stop discassembly 128 contains a gear train and operates similarly to the stopdisc assemblies 94 and 88 of the first preferred embodiment. However, inthis case, instead of driving a slant disc when the stop disc 130 isstopped by an electromagnetic catch, the second shaft 126 is driven andmoves backwards relative to the shaft 124. Rotary movement of the shaft126 also controls the rotary position of a pivot ring assembly 132 whichis firmly attached to the second shaft 126. An output adaptor 134 ismounted on the shaft 124, held in place by a clamp ring 136, and causedto rotate with the shaft 124 by a drive disc 138.

80. A second stop disc assembly 130, containing a gear train, is mountedon the second shaft 126 and operates similar to stop discs 94 and 96 ofthe first preferred embodiment with the output of the gear train drivinga single slant disc 140 detailed in FIG. 10c. When stop disc 130 isstopped, the slant disc 140 moves backward in relation to shaft 124. Theaxial force produced by an axially mounted drawbar 58, note again FIG.4, causes the output adaptor 134, through the pivot ring 132 to assumean angle to the shaft 124 depending upon the rotated position of slantdisc 140.

81. Referring to FIG. 10b, there is shown a cross-sectional view ofautomatic alignment mechanism rotated 90 degrees counterclockwise aboutthe input axis of FIG. 10a. The pivot ring 132 does not rest against thestop disc assembly 130 over its entire surface. Rather, there are 2“bumps” diametrically placed on the face of the pivot ring 132 whichrest against the stop disc assembly 130. This allows the slant disc 140to transmit its angle to the pivot ring 132 but allows the pivot ring132 to pivot on its fixed axis pins 142. Thus, once set, thecompensation vector necessary (explained in more detail with referenceto FIGS. 11a and 11 b) necessary for alignment does not change when theslant disc 140 varies the output compensation angle. Referring to FIG.10d, there is shown the pivot ring assembly 132 in more detail.Specifically, by making one of the “bumps” on the pivot ring 132 acertain amount larger than the other, the pivot ring 132 is madeperpendicular to the shaft 124 at one extreme position of slant disc 140and at maximum compensation angle at the other extreme. A ½ degreevariance, for example, is provided between the bumps as shown in FIG.10d. Similarly, a ½ degree variance between the bumps on slant disc 140is provided as shown in FIG. 10c. Thus, when the slant disc 140 and thepivot ring 132 are placed against the disc 130 with the ½ degree faceangles complementing each other, a 0 degree runout between the input tooutput adapters is achieved. On the other hand, when the discs arerotated 180 degrees relative to each other, the angles oppose each otherand the runout input and output is 1 degree.

82. Referring now to FIGS. 11a and 11 b, there is shown a schematicdepicting the relationship between the compensation vector, compensationangle, and pivot axis contemplated by the alignment device of thepresent invention. Generally, two parameters are of importance whenaligning the rotating shafts of the lathe and brake hub. The firstparameter referred to as the “compensation vector” is defined by the arotation position at which the lateral runout deflection of the brakelathe is the greatest. The second parameter referred to as the“compensation angle” is defined by the angle that the input adaptor andthe output adaptor must assume in relation to each other in order tocompensate for this lateral runout. In the second embodiment, thecompensation vector and the compensation angle can be adjustedseparately as shown in FIG. 10a.

83. However, in the first and third (described below) embodiments, thecompensation vector is adjusted by “stopping” simultaneously the inputdisc and output disc. This does not affect the relative rotationalpositions of the discs and thus does not change the input to outputangle. Rather, adjustment of the compensation vector only changes therotational position where the disc's angle changing capability iseffective. The compensation angle is adjusted by “stopping” the outputdisc only, which rotates it in relation to the input disc and thuschanges the input to output angle.

84. Referring now to FIGS. 12 through 16 there is shown a thirdpreferred embodiment of the present invention. The third preferredembodiment is similar to the first preferred embodiment differing inthat the slant discs are separated from each other and from the inputand output adapters by pin roller thrust bearings to allow free rotationof these elements under normal axial pressure; the rotationalpositioning of the slant discs relative to each other and to the inputand output adapters is performed by actuating four “starwheels” whichdrive the slant discs through gear trains; and both forward and reversepositioning capability of the slant discs is provided which allows aconsiderable decrease in time to final alignment.

85. Referring to FIG. 12, there is a cross-sectional drawing of anautomatic alignment coupling or mechanism 144 that occupies the sameposition of the mechanism 50 of the first embodiment shown in FIG. 4. Aninput adaptor 146 attaches to and is rotationally driven by the outputshaft of the brake lathe. Adaptor 146 contains two “starwheels” 180 and182 which drive gear trains which ultimately position an input slantdisc 152, described in more detail with reference to FIG. 13a. Anadaptor cover 154 serves as a cover for the gearing and as a bearingsurface which runs perpendicularly true to the shaft 156 which isattached to input adaptor 146.

86. Thrust bearing assembly 158, with its two race rings, are placebetween input slant disc 152 and the bearing surface of adaptor cover154. This bearing assembly allows free rotation of the slant disc 152relative to the input adaptor 146 and the attached shaft 156 whileautomatic alignment mechanism is under axial pressure in normaloperation. Output slant disc 160 is separated from slant disc 152 by athrust bearing assembly 162 identical to thrust bearing assembly 158 toallow output slant disc 160 to freely rotate under axial pressure. Athird thrust bearing assembly 164 is placed between output slant disc160 and the output adaptor cover 166, again to allow free rotation ofthe output slant disc 160.

87. Output adaptor 168 contains the same “starwheel” and gearingassembly as does input adaptor 146. It differs in that it is free tomove to an angle that varies as much as 1 degree, for example, fromperpendicular to the shaft 156 axis. Output adaptor 158 is rotationallycoupled to the shaft 156 by means of a drive arm 170 that is keyed tothe shaft 156. Referring to FIG. 13b, there is shown the input side ofthe output adaptor 168 without the starwheel and gears for clarity. Thedrive arm 170 is shown in place with key 172 coupling it to the shaft156. A drive pin 174 is positioned in the output adaptor 168 and fits inthe slot 176 of the drive arm 170 to cause the output adaptor 168 torotate with the shaft 156 while allowing the output adaptor 168 to tipangularly in relation to the shaft 156.

88. Referring to FIG. 12, a collar 178 serves as both a bearing surfacefor the inside diameter of output adaptor 168 and a shoulder to preventthe disassembly of the parts when the auto align mechanism is notoperating under axial pressure. A wave washer 153 or the like is placedbetween input slant disc 152 and input adaptor 146 in order to providesome friction so that rotation of output slant disc 160 will not causeunwanted rotation of the input slant disc 152.

89. Referring to FIG. 13a, input and output adaptor assembliespreferably comprise a forward starwheel 180 that is coupled to a gear184 having, for example, 18 teeth. Gear 184 meshes with a gear 186having, for example, 56 teeth. Gear 186 is coupled to gear 188 having,for example, 18 teeth. Gear 188 meshes with a ring gear 190 having, forexample, 140 teeth. The ring gear 190 is operably attached to arespective slant disc 152 or 160 as shown in FIG. 12.

90. Referring again to FIG. 13a, when the entire auto align mechanismrotates at 2.05 RPS, for example, in normal operation, the starwheel 180can be caused to rotate by “catching” one or more teeth as the starwheel180 passes by a fixed stop mechanism comprising an electromagnetic catchor the like. Thus, a slant disc can be caused to rotate in incrementsrelative to the auto align mechanism. The reverse starwheel 182 and gearassembly operates similarly to the forward starwheel 180 and gearassembly except that an additional gear 192 causes the slant disc torotate in the opposite direction when the starwheel 182 is rotated.

91. Referring to FIG. 14, there is shown starwheel stop mechanism 194that comprises a toothed catch member 196 and a magnetic element such assolenoid 198 or the like. Preferably, one stop mechanism 194 is providedto operate in conjunction with the input adaptor 146 and another isprovided to operate in conjunction with the output adaptor 168. Thetoothed member 196 may contain one or more teeth so as to “catch” one ormore starwheel teeth each rotation of the automatic alignment mechanism.Note that the teeth of the member 196 are spaced apart so as to allowtime to lift the toothed member between starwheel contact to control theamount of starwheel rotation per auto align mechanism rotation.

92. As the starwheels on each adaptor 146 and 168 are in line, theaction of the starwheel “catch” or “stop” mechanisms have to be timed insynchronism with the rotation of the auto align mechanism in order thatonly the desired starwheel, (i.e. forward starwheel 180 or reversestarwheel 182) is actuated. FIG. 15 shows an exemplary timing controldiagram for the starwheel stop mechanism 194. As shown, a halltransducer or the like timing pulse is used as a time reference point.

93. Referring to FIG. 16, there is shown a novel alignment process flowdiagram as specifically exemplified with reference to the thirdpreferred embodiment. It is noted that any suitable measurement devicecould be used in conjunction with the alignment mechanism. Preferably,however, a novel sensing and measuring device of the present inventionas described below is utilized to operate in conjunction with the novelalignment mechanisms described above. It is also noted that although thealignment process is shown and described in FIG. 16 with reference tothe third preferred embodiment, the general process algorithm isapplicable to all embodiments of the present invention. Furthermore, thenovel alignment apparatus and process may also be advantageouslyutilized in other practical applications in order to align twoconcentrically rotating shafts.

94. In general, the flow diagram of FIG. 16 shows a sequence of “trialand error” adjustments wherein an adjustment is initially made bystopping a star wheel on one of the adapters and measuring the change inthe runout or alignment. If the runout improved, an additionaladjustment is ordered in the same direction. If the alignment worsens,an adjustment in the opposite direction is ordered. This process isrepeated until the alignment is corrected to within specifications andthe lathe shaft and hub axes are aligned. Two distinct periods ofadjustment are employed in the present invention. A first cycle takesplace wherein large adjustments are made in the orientation of slantdiscs 152 and 160 to more significantly change the alignment of theshaft and hub axes, and thereby correct runout. Once alignment reaches apredetermined low level, finer adjustments are made to correct runout towithin specified tolerances.

95. Referring to FIG. 16, the runout correction process begins withinitialization of several variables. At step 302, the stop level of stopmechanism 194 is set to three actuations of the starwheels. Thisprovides the large movements of slant discs 152 and 160 at the beginningof the adjustment cycle. Also at step 302, several internal counts andlimits are initialized including flag Z, flag D, and a try counter.Also, the initial specification value is supplied which represents anacceptable level of runout. Typically, this value is set to be in theorder of 0.001 inch. The try counter operates when runout drops to a“Min” value. This counter causes the value of “Spec” to increase afterthe system tries to reach the present “Spec” runout value a programmednumber of tries or cycles. This prevents the system from trying toforever reach a runout value that is impossible given the circumstances.

96. An initial evaluation of the runout is made at step 303 and thisquantity is stored a R-pres, representative of a base value of therunout. Step 304 provides for a comparison of the measured runout with arunout measurement that conforms to specification, usually on the orderof 0.001 inches as noted above. If the runout is less than 0.001 inches,the runout is determined to fall within specified tolerances (“Spec”)and no further compensation is required as is indicated in step 310. Atstep 306, the value of R-pres is copied into the memory location ofR-last. Next, if R-pres does not exceed a predetermined level “Min”(step 307), the stop mechanism 196 is set to stop one tooth of thestarwheel 180 or 182 per revolution as indicated in step 308. At step309, the try count is incremented and at step 310 the try count isevaluated such that of the try count is at a limit, the runout “Spec”limit is raised (step 311) and the try count is reset to 0 (step 312).The higher “Spec” limit usually consist of a value that is stillacceptable but less preferred than the original “Spec” limit (e.g. 0.001inch). For example, 0.003 inch higher “Spec” is acceptable.

97. At step 313, the flag Z is tested to determine if starwheelactuation has run in both directions. That is, whether both output 180(forward) and 182 (reverse) starwheel have been activated. At step 10,if the Z flag has not been toggled twice, then the program proceeds tostep 315 to determine the state of flag D and if the Z flag has beentoggled has been toggled twice, then step 314 toggles flag D. If Dequals 0, then the output only starwheel is actuated changing the“compensation angle” of the system. If D equals 1, both the output andinput starwheels are actuated to change the “compensation vector” of thesystem.

98. At step 318, the system waits for one of two revolutions of thelathe (depending on whether the accelerometer is operating in mode 1 ormode 2 as described below) before proceeding in order to allowtransients introduced by the last starwheel adjustment to dissipate. Atstep 319, the runout is again measured. In step 320, if runout is lessthan Spec (e.g. 0.001 or 0.003 inches), the system progresses to step305 and the runout adjustment is complete. At step 321, the runout fromthe present measurement, R-pres, is compared to the runout from the lastmeasurement, R-last. If R-pres is less than R-last, the systemprogresses to step 306 where R-pres is copied into R-last and theprocess continues through another iteration and the same starwheelpreviously actuated is again actuated. If, on the other hand, R-pres isgreater than R-last, the system progresses to step 322 where flag Z istoggled to its opposite state. Control is then passed back to step 306where in turn the other starwheel of the starwheel pair is actuated tocause rotation of the adjustment disc in an opposite direction.

99. In this manner, the system employs a trial and error approach toreducing runout. As long as the runout-continues to decrease, additionalactuations of the same starwheel occur. However, if runout worsens, theopposite starwheel is actuated to begin to correct the runout. If thisforward and reverse cycle does not improve the runout, the compensationvector is adjusted by moving both of the input and output adjustmentdiscs. A microprocessor and suitable circuitry controls the operation ofthe present invention as described below with reference to FIG. 23.

100. The alignment adjustment system of the present invention is asubstantial improvement over prior art devices and techniques. Once theappropriate sensor and measuring system is properly secured (forexample, one of the novel systems disclosed below), the automaticalignment system provides for mechanical compensation of the totallateral runout present in the disc brake assembly. Specifically, thealignment system adjusts the alignment of the brake lathe component withrespect to a vehicle hub in order to compensate for lateral runout.This, in turn, ensures that the cutting head 36 is placed perpendicularto the rotation axis of the hub 44.

101. Lateral Runout Measurement and Control System

102. The apparatus and method for runout compensation disclosed aboveserves to align the lathe and rotor axes under the direction of anangular runout sensing and control mechanism of the present invention.However, it is to be understood that the runout sensing and controlmechanism described herein may be used with any suitable sensor that isresponsive to angular acceleration or variations in the distance betweenthe cutting tool end of the lathe body and the auto under consideration.In the present invention, the runout sensor preferable takes the form ofan electronic accelerometer. The novel measurement and control systemmay also be advantageously utilized in other practical applications inorder to align two concentrically attached rotating shafts.

103. Referring to FIGS. 17 and 18, there is shown a brake latheassembly, coupled through an auto align mechanism of the type shown anddescribed above to a wheel axle. The lathe tools are shown at the end ofthe brake assembly mechanism arm, arranged to move from the center ofthe brake disc toward the outside while the drive motor causes the wheeland brake disc to rotate as described above. The solid lines show themechanism position when the wheel axis and the lathe axis are inalignment. Under these conditions the lathe tools cut the disc surfacessmoothly.

104. However, where runout is present, the lathe will rotate back andforth when in use. The dotted lines show the wobbling of the lathemechanism when the wheel axis and the lathe axis are misaligned (in thedrawing the runout is greatly exaggerated). obviously, with the lathemechanism and tools wobbling the brake disc lateral runout is cut intothe rotor and such operation is not acceptable. Note that at the “X”point the mechanism changes its position not only linearly but also in arotational sense perpendicular to the drive axis. That is, the angle ofthe mechanism changes cyclically as the wheel is rotated.

105. It is at this point that the sensing devices of the runout sensingand control mechanism of the present invention are preferably placed inorder optimize measurement sensitivity. Preferably, the sensing devicesare additionally positioned such that the internal rotor axis (asdescribed below) is perpendicular to the lathe drive axis.

106. Referring to FIG. 18, there is another misalignment mode which canoccur when the wheel axis and the lathe axis are in misalignment.This-is off-center misalignment. With this, the motion of the lathemechanism contains only linear components while no angular runoutoccurs, therefore no rotational motion perpendicular to the drive axisoccurs. This runout motion does not detract significantly from thesmooth cutting of the brake disc surface and can be allowed. For thisreason, it is an objective that the sensing device of the presentinvention sense only the rotation components impressed upon its housingwhile rejecting all linear motions.

107. A variety of different sensing configurations can be used as a partof the runout sensing and control mechanism of the present invention.Generally, there are two operating modes employed in utilizing therotary accelerometer as a runout detector. In a first mode the naturalfrequency of resonant motion of the rotor transducer is configured (asexplained below) to be about 1.5 times the frequency of lathe rotation.In this mode configuration, the accelerometer achieves the most rapidfollowing of the changes in runout and therefore, often the most rapidalignment due to damping inherent in the frequency differential.However, the runout sensitivity of the system is less than ½ that ofmode two. In mode two, the natural frequency of resonant motion of therotor-transducer is configured to be below the frequency of latherotation. This provides the most sensitivity to runout and helps tosuppress harmonics in the runout motion which can cause alignmentuncertainty. However, this mode configuration is slower in followingchanges in runout which may slow alignment as compared to modeconfiguration one. In any event, the natural frequency of resonantmotion should never by placed at the frequency of lathe rotation becauseoperating in resonance with the lathe results in an unnatural buildup ofrotor-transducer motion which doesn't allow the accelerometer output toimmediately follow the runout magnitude, seriously slowing the alignmentprocess.

108. Independent of the operation mode, several considerations arerelevant in implementing each of the embodiments of the inventiveaccelerometer. First, the accelerometer rotor should be completelybalanced in order to insure measurement of rotational accelerations,while rejecting linear accelerations. Second, the rotation of the rotorshould be physically limited such that rotation only occurs within thesensitive area of the transducer. Finally, the natural frequency ofresonant motion of the rotor-transducer should be configured to operatein either mode 1 or 2 as already discussed above. In this regard, thenatural frequency depends on several variable including mass of therotor, diameter of the rotor, and characteristics of a spring element(e.g. music wire).

109. The accelerometer embodiment using a piezo-electric element as asensor (described below) is best suited to operating where the naturalfrequency of resonant motion is about 1.5 times the frequency of latherotation because some force is required to bend the element tending tocause a high spring rate. The other transducer schemes described beloware non-contact devices and the spring rate can be dictated by springselection. In this regard, these embodiments are well suited to eithermode one or mode two operation.

110. In a first embodiment as shown in FIG. 19 there is a rotaryaccelerometer sensor 210. Sensor 210 comprises a housing 212 thatencloses a rotor 214 mounted for rotation on bearings 216 and 218. Therotor 214 is carefully balanced so that all accelerations exceptrotational cause no rotation of the rotor 214. Rotation of the rotor 214is sensed by a piezo electric element 220 which is mounted between thehousing 212 and the rotor 214 and is bent by any rotation of the rotor214 producing a voltage proportional to the magnitude of bending.Rotation of the rotor 214 is limited to protect the piezo electricelement 220 by piezo element mount 220 in the slot 222 in the rotor 214.

111. The piezo disc 220 and the rotor 214 operate as a spring and masssystem having a natural frequency of resonant motion as generallydescribed above. In this spring/mass system, the rotor constitutes themass and the piezo disc 220 constitutes the spring. In this embodiment,the system operates in mode one such that the rotor mass and diameterand the piezo spring quality is adjusted to obtain a frequency in theorder of 1.5 times the frequency of lathe rotation. It is of furtherimportance that the rotor 11 be suitably damped in order to minimize thesettling time. This can be achieved by filling the housing 10 with aviscous fluid and sealing the housing with a cover. Alternatively,damping can be provided by using a clinging viscous material in thebearings 12 and 13. Other damping techniques are considered to be withinthe scope of the invention. A resultant signal, whose amplitude isproportional to the magnitude of the angular runout, is then directed toa control system as described below with reference to FIG. 23.

112. The sensing device of the present invention may also be configuredwith alternative transducing elements that provide a suitable controlsignal. For example, the inventive sensor may be sensing elementcomprising an accelerometer with a tuned coil oscillator. Referring toFIG. 22, the spring component of this system comprises a wire(preferably music or piano wire) 244 that is attached to the body 256and rotor 246 as shown. The wire may be attached by any suitable meanssuch as, for example, brackets as shown in FIG. 22. As previously noted,the natural frequency of resonant motion of the rotor-transducer isdependant on the mass and diameter of the rotor and springcharacteristics. When using a music wire 244 to control frequency ashown, the tension of the wire 244 and the wire 244 gage are manipulatedto vary the frequency. For example, to achieve a natural frequency orresonant motion of the rotor-transducer that is below the frequency oflathe rotation, a gage in the range of approximately 9-10 thousandths isutilized and the wire tension is configured to be relatively loose. Onthe other hand, to achieve a natural frequency of resonant motion of therotor-transducer that is about 1.5 times the frequency of latherotation, a gage in the range of approximately 16 thousandths isutilized and the wire tension is configured to be relatively tight.

113. A ferrite or the like disc 248 is placed in the periphery of therotor 246 adjacent to a housing-mounted coil 250 which forms the -L- ofan oscillator circuit 252. When the rotor 246 turns, the ferrite disc248 moves in relation to the coil 250, causing a change in theinductance of the oscillator coil 250, thus a change in the frequency ofoscillation. A discriminator 254 converts the change in frequency ofoscillation to a varying DC voltage. This varying voltage reflects therotation of the accelerometer housing 256. The signal is then forwardedto a control system as described below with reference to FIG. 23.

114. As previously noted, it is important to configure the rotor suchthat it is balanced. In order to limit the rotation of the rotor suchthat rotation only occurs within the sensitive area of the transducer, acounterbore 245 is provided that cooperates with a pin 247 to limitrotor rotation as appropriate. Other limiting means are within the scopeof the invention.

115. In an alternative embodiment the sensing device is an accelerometerwith an magnet-hall effect transducer as shown in FIG. 20. In thisconfiguration, a leaf spring 222 has a spring rate which, in combinationwith the inertia of the rotor 224, provides a resonant frequency about1.5 times the rotational rate of the brake lathe shaft (i.e. operationin mode one). Alternatively, the accelerometer of this embodiment couldbe configured to operate in mode one or two using a music wire asdescribed above. A magnet 226 is placed in the periphery of the rotor224. A hall effect transducer 228 with a linear characteristic is placedin the housing 230 adjacent to the magnet 226 such that rotary motion ofthe rotor is reflected in the output voltage of the hall effecttransducer 228. The magnitude of the AC voltage at the output of thehall effect transducer 228 is a reflection of the rotary motion of theaccelerometer housing 230 that is attached to the lathe, preferably atthe position identified with reference to FIGS. 17 and 18. The resultingsignal is forwarded to a control system as described below withreference to FIG. 23.

116. In yet another alternative embodiment, the sensing elementcomprises an accelerometer with an infrared generator. Referring to FIG.21 and 21 a, there is shown a leaf spring 232 that preferably has aspring rate which, in combination with the inertia of a rotor 234,provides a resonant frequency about 1.5 times the rotational rate of thebrake lathe shaft. Again, this accelerometer could alternatively beconfigured to operate in mode one or two using a music wire as describedabove. An infrared generator diode 236 is placed facing an infrareddetector diode 238 on the housing 240 near the periphery of the rotor234.

117. A shutter 242 is attached to the rotor 234 and projects between theIR generator 236 and IR detector 238 such that rotary motion of therotor 234 varies the amount of radiant energy transferred, causing thevoltage out of the IR detector 238 to reflect the magnitude of housing240 rotation. Again, this measurement reflecting the runout of the disccoupling. The signal is forwarded to a control system as described belowwith reference to FIG. 23.

118. The runout sensing and control mechanism of the present inventionfurther comprises a control circuit which is now described withreference to FIG. 23. Transducer 400 may be advantageously comprised ofany of the several different types of sensors designed to evaluate therotational acceleration of the lathe as set forth below. Because lateralrunout manifests itself in varying rotational motion imparted to thelathe, any sensor arrangement capable of producing an accuratequalitative measure of rotational acceleration may be utilized. Thepreferred structured herein utilizes an inertial disc and piezo electricelement as transducer 400, as described in greater detail below. Theoutput of transducer 400 is fed to amplifier 402 and then to rectifier404. Because runout produces a cyclical motion in the lathe, the signalproduced by transducer 400 is sinusoidal in nature; however, at lowerrunout levels other wave forms could resonate. After amplification byamplifier 402 and rectification by full wave rectifier 403, the peakrunout signal is feed to an integrator 404 that is reset 406 each latherotation cycle as indicated. The signal is then sent to a sample andhold circuit 407. A hall pickup timer 405 produces a synchronizationsignal as shown. The output is then transmitted to A/D converter 408which samples the voltage level and produces a digital representationthereof. The output of A/D converter 408 is passed to both latch 410 andmicroprocessor 412. The output of latch 410 is also provided tomicroprocessor 412. Latch 410 is a conventional sample and hold latchand is clocked just prior to the time A/D converter 408 presents a newsample. In this manner, both the current sample taken by A/D converter408 and the last sample taken by A/D converter 408 are available tomicroprocessor 412. At the output of microprocessor 412 there isprovided amplifiers 414 and 416 which are used to drive stop mechanism196.

119. Taken in conjunction with the algorithm set forth in FIG. 16,microprocessor 412 is thus provided with a stream of samples of therunout of the rotor under consideration, together with a samplerepresenting the last historical value of the runout. In this manner,the microprocessor implements the trial and error approach describedabove with respect to FIG. 16.

SUMMARY OF MAJOR ADVANTAGES OF THE INVENTION

120. After reading and understanding the foregoing detailed descriptionof an inventive on-car brake lathe with automatic alignment system andprocess in accordance with preferred embodiments of the invention, itwill be appreciated that several distinct advantages of the subjectalignment system and process are obtained.

121. Without attempting to set forth all of the desirable features ofthe instant on-car disc brake lathe with automatic alignment system, atleast some of the major advantages include providing an on-car discbrake lathe having an automated alignment assembly 50 that includes apair of adjustment disc assemblies that are positioned between an inputadaptor 66, 122, 146 and an output adaptor 78, 134, 168. Each of theadjustment disc assemblies includes an adjustment disc 90, 92, 140, 152,160 and associated stop disc. An electromagnetic catch 98, 100 or thelike is operably associated with each of the stop discs 94, 96 andoperates in response to a control signal issued from a control system.When the rotation of one of the stop discs is stopped, rotationalmovement of the lathe drive shaft is transferred, through appropriategearing, to a respective adjustment disc to change the relative positionof the lathe drive axis and the vehicle hub axis.

122. In a preferred embodiment, the control algorithm and alignmentprocess of the present comprises a series of “trial and error”adjustment inquiries in order to compensate for runout. As the lathebegins to rotate and the Hall signal provides a timing signal, and therunout level is evaluated and if within the “Spec” limit, normally0.001″, the alignment goes to the “Low-Ready to Cut” light and theprogram ends. If the runout is above the “Spec” limit, an actuation ofthe output forward starwheel is ordered. The runout is evaluated and iflower, added actuations of the same starwheel are ordered until anactuation causes the runout to increase. At this point, if the runout isstill above the “Spec” limit, an actuation of the output reversestarwheel is ordered. If the runout is lower, further such actuationsare ordered until an actuation causes the runout to increase. Theprevious two actions adjusts the “compensation angle.” At this point, ifthe runout is still above the “Spec” limit, an actuation of both theoutput and the input forward starwheels in tandem is ordered. Thisaction adjusts the “compensation vector.” The runout is evaluated and iflower, further actuations of the output and input forward starwheels intandem are ordered until an actuation causes the runout to increase.

123. At this point, if the runout is still above the “Spec”, anactuation of the output and input reverse starwheels in tandem isordered. The runout is evaluated and if lower, further such actuationsare ordered. If an actuation causes a runout increase, and if the runoutis still above the “Spec” limit, the starwheel actuations revert to theoutput starwheels only mode again as described previously. Thisactuation sequence continues as above, trial and error, until the runoutis reduced to the “Spec” limit, where the “Ready to Cut” light isilluminated and the program ceases.

124. A count is kept of the number of tries to reach the “Spec” runoutlevel and when a preset number of tries is exceeded, the acceptancelevel is raised to about 0.003″ and if the runout is within this level,a “Ready to Cut” light is illuminated and the program ceases. If thisnew higher runout level can not be reached after a preset number oftries, a “Out of Spec” lite is illuminated and the program ceases. Theoperator is directed to check the lathe coupling to the brake disc huband to check for bad wheel bearings, correct the problem and try thealignment cycle again. Depending on the level of runout, the system canbe controlled such that 3 starwheel teeth are “caught” in each starwheelactuation for rapid adjustment or only 1 starwheel tooth is caught eachactuation allowing fine adjustment of the runout level.

125. In describing the invention, reference has been made to a preferredembodiment and illustrative advantages of the invention. Those skilledin the art, however, and familiar with the instant disclosure of thesubject invention, may recognize additions, deletions, modifications,substitutions and other changes which fall within the purview of thesubject invention.

What is claimed:
 1. An on-car disc brake lathe system for resurfacingbrake disc of a vehicle brake assembly, said brake lathe comprising alathe body with a driving motor, a cutting head operably attached tosaid body, and a drive shaft, said on-car brake lathe system furtherdefined by an alignment system comprising: an input adaptor configuredto rotate with said drive shaft; an output adaptor configured to rotatewith said drive shaft; at least one stop disc positioned between saidinput and output adaptor and operable to follow the rotation of saiddrive shaft and operable to rotate relative to the rotation of saiddrive shaft; and at least one adjustment disc associated with arespective said at least one stop disc and operable to rotate inresponse to the relative rotation of said at least one stop disc, saidat least one adjustment disc configured to be capable of adjusting theaxial alignment of said drive shaft with respect to an axis of rotationof a brake disc.
 2. An on-car disc brake lathe system as defined inclaim 1 wherein: at least one stop mechanism associated with said atleast one said stop disc wherein said stop mechanism moves from a firststop position and a second withdrawn position such that when said stopmechanism is in said first stop position, said stop disc is caused torotate relative to the rotation of said drive shaft.
 3. An on-car discbrake lathe system as defined in claim 2 wherein: said at least one stopdisc comprises a pair of stop discs rotatably secured to said inputadaptor such that said pair of stop disc rotate with said input adaptorwhen said associated stop mechanism is in said second withdrawn positionand at least one of said pair of stop discs rotates relative to saidinput adapter when said associated stop mechanism is in its first stopposition.
 4. An on-car disc brake lathe system as defined in claim 3wherein: said at least one stop disc comprises a further pair of stopdiscs rotatably secured to said output adaptor such that said furtherpair of stop disc rotate with said output adaptor when said associatedstop mechanism is in said second withdrawn position and at least one ofsaid further pair of stop discs rotates relative to said input adapterwhen said associated stop mechanism is in its first stop position.
 5. Anon-car disc brake lathe system as defined in claim 4 wherein: said atleast one adjustment disc comprises a first adjustment disc operablyassociated with said pair of stop discs and a second adjustment discoperably associated with said further pair of stop disc.
 6. An on-cardisc brake lathe system as defined in claim 5 wherein: said first andsecond adjustment disc comprise slant discs having a slanted surfacesuch that said slanted surfaces of said slant discs are opposed to eachother in an abutting relationship.
 7. An on-car disc brake lathe systemas defined in claim 5 further comprising: a first gear train operablyassociated with said pair of stop discs and a second gear train operablyassociated with said further pair of stop discs, said gear trainsconfigured to follow the movement of said respective pair of stop discs,said first gear train being operably associated with said firstadjustment disc and said second gear train being operably associatedwith said second adjustment disc.
 8. An on-car disc brake lathe systemas defined in claim 7 wherein said first and second gear trains areconfigured such that when the associated stop mechanism stops one ofsaid respective pair of stop discs, the respective adjustment disc iscaused to rotate in a first rotational direction and when the stopmechanism stops the other of said respective pair of stop discs, therespective adjustment disc is caused to rotate in a rotational directionopposite to the first rotational direction.
 9. An on-car disc brakelathe system as defined in claim 8 further comprising: a ring gearoperably connected to the first slant disc such that movement of saidring gear is followed by said slant disc.
 10. An on-car disc brake lathesystem as defined in claim 5 wherein said gear train comprises a firstgear section associated with one of said pair of stop discs and a secondgear section associated with the other of said stop discs wherein: saidfirst gear section comprises a first gear element operable to rotatewith a respective stop disc, a second gear element meshed with saidfirst gear element, and a third gear element operable to rotate withsaid second gear element, said third gear element being meshed with saidring gear such that rotation of the associated stop disc causesrespective rotation of the first, second, and third gear elementsthereby causing rotation of the ring gear in said first rotationaldirectional; said second gear section comprises a first gear elementoperable to rotate with a respective stop disc, a second gear elementmeshed with said first gear element, and a third gear element meshedwith said second gear element, and fourth gear element operable torotate with said third gear element, said fourth gear element beingmeshed with said ring gear such that rotation of the associated stopdisc causes respective rotation of the first, second, third, and fourthgear elements thereby causing rotation of the ring gear in a rotationaldirection opposite said first rotational directional.
 11. An on-car discbrake lathe system as defined in claim 10 further comprising a drive armkeyed to rotate with said drive shaft, said drive arm rotationallycoupled to the output adaptor such that said output adaptor follows therotation of said drive arm, said output adapter further configured to becapable of rotating about a vertical axis perpendicular to the centralaxis of said drive shaft.
 12. An on-car disc brake lathe system asdefined in claim 2 wherein said at least one stop disc comprisesstarwheels having a plurality of protruding teeth.
 13. An on-car discbrake lathe system as defined in claim 12 wherein said stop mechanismcomprises an electromagnetic element and a toothed catch member operableto engage at least one of said plurality of teeth of said star wheels.14. An on-car disc brake lathe system as defined in claim 13 furthercomprising means for timing the actuation of the stop mechanism suchthat the toothed catch moves into its first stop position to contact aspecified at least one stop disc upon receipt of a control signal. 15.An on-car disc brake lathe system as defined in claim 1 furthercomprising: a draw bar extending through the body of said lathe and saidalignment system and operable for connection to a hub adapter of avehicle brake assembly.
 16. An on-car disc brake lathe system as definedin claim 1 further comprising means for measuring the lateral runout ofa brake disc, said means for measuring producing an electrical controlsignal that actuates said stop mechanism.
 17. An alignment assembly foruse in an on-car disc brake lathe system for resurfacing brake disc of avehicle brake assembly, said alignment system comprising: an inputadaptor configured to rotate with a drive shaft of a brake lathe system;an output adaptor configured to rotate with a drive shaft of a brakelathe system; at least one disc positioned between said input and outputadaptor and operable to follow the rotation of said drive shaft andoperable to rotate relative to the rotation of said drive shaft; and atleast one adjustment disc associated with a respective said at least onedisc and operable to rotate in response to the relative rotation of saidat least one disc, said at least one adjustment disc configured to becapable of adjusting the relative axial alignment of said input adaptorwith said output adaptor.
 18. An on-car disc brake lathe system asdefined in claim 17 wherein: said at least one disc comprises a pair ofdiscs rotatably secured to said input adaptor such that said pair ofdisc rotate with said input adaptor and can be caused to rotate relativeto said input adapter.
 19. An on-car disc brake lathe system as definedin claim 18 wherein: said at least one disc comprises a further pair ofdiscs rotatably secured to said output adaptor such that said furtherpair of disc rotate with said output adaptor and can be caused to rotaterelative to said output adapter.
 20. An on-car disc brake lathe systemas defined in claim 19 wherein: said at least one adjustment disccomprises a first adjustment disc operably associated with said pair ofdiscs and a second adjustment disc operably associated with said furtherpair of stop disc, said first and second adjustment disc comprise slantdiscs having a slanted surface such that said slanted surfaces of saidslant discs are opposed to each other in an abutting relationship. 21.An on-car disc brake lathe system as defined in claim 20 furthercomprising: a first gear train operably associated with said pair ofstop discs and a second gear train operably associated with said furtherpair of stop discs, said gear trains configured to follow the movementof said respective pair of stop discs, said first gear train beingoperably associated with said first adjustment disc and said second geartrain being operably associated with said second adjustment disc.
 22. Anon-car disc brake lathe system as defined in claim 21 furthercomprising: a first adapter cover adjacent to said input adapter and asecond adapter cover adjacent said output adapter, said input and outputadapters, adapter covers, and adjustment discs having a concentric axisof rotation.
 23. An on-car disc brake lathe system as defined in claim22 further comprising: thrust bearings positioned between surfaces ofsaid adapter and adjacent surfaces of said adjustment discs.
 24. Anapparatus for aligning the axes of two rotating shafts comprising: afirst input adaptor configured to rotate with one of said shafts; asecond output adaptor configured to rotate with the other of saidshafts; at least one stop disc positioned between said input and outputadaptor and operable to follow the rotation of the first shaft andoperable to rotate relative to the rotation of said first shaft; and atleast one adjustment disc associated with a respective said at least onestop disc and operable to rotate in response to the relative rotation ofsaid at least one stop disc, said at least one adjustment discconfigured to be capable of adjusting the axial alignment of said firstshaft with respect to an axis of rotation of said second shaft.
 25. Amethod for adjusting the alignment between a vehicle brake assembly andan on-car disc brake lathe having a driving motor, a cutting headoperably attached to said body, and a drive shaft wherein said on-cardisc brake lathe is operably attached to the hub of a vehicle brakeassembly in order to compensate for runout comprising the steps of: (a)measuring the rotational acceleration of the lathe that reflects tolateral runout of the attachment between the vehicle brake assembly andthe on-car disc brake lathe; (b) comparing the measured runout value ofthe lathe with a stored acceptable runout limit and cease furtheradjustment if the measured value is below an acceptable limit; (c)adjusting in a first direction the relative axial position of the lathedrive shaft with respect to the axis of rotation of the vehicle brakeassembly; (d) repeating measuring step (a), and if the runout isdetermined to be lower in the repetition, repeat step (c) until therunout is determined to be increase; (e) adjusting in a second directionthe relative axial position of the lathe drive shaft with respect to theaxis of rotation of the vehicle brake assembly; (f) repeating measuringstep (a), and if the runout is determined to be lower in the repetition,repeat step (c).
 26. A method for adjusting the alignment in order tocompensate for runout between a vehicle brake assembly and an on-cardisc brake lathe having a driving motor, a cutting head operablyattached to said body, and a drive shaft wherein said on-car disc brakelathe is operably attached to the hub of a vehicle brake assembly, saidbrake lathe further including a alignment system having an input adaptorand an output adaptor configured to rotate with said drive shaft, and afirst pair and second pair of stop discs rotatably engaged to respectivesaid input and output adapters, said first pair of stop disc beingoperably engaged with a first adjustment disc and said second pair ofstop disc being operably engaged with a second adjustment disc such thatrotation of one of said pair of stop disc causes a respective adjustmentdisc to rotate in a first direction and rotation of the other of saidpair of stop disc causes a respective adjustment disc to rotate in asecond direction opposite to the first direction, said method comprisingthe steps of: (a) measuring the rotational acceleration of the lathethat reflects to lateral runout of the attachment between the vehiclebrake assembly and the on-car disc brake lathe; (b) comparing themeasured runout value of the lathe with a stored acceptable runout limitand cease further adjustment if the measured value is below anacceptable limit; (c) rotating one of the pair of the stop disc of saidoutput adaptor a predetermined degree and repeating measuring step (a)and comparing step (b), and if the runout is determined to be lower inthe repetition, continue to rotate and repeat step (a) and (b) until therunout is determined to be increase; and (d) rotating the other of thepair of the stop disc of said output adaptor a predetermined degree andrepeating measuring step (a) and comparing step (b), and if the runoutis determined to be lower in the repetition, continue to rotate andrepeat step (a) and (b) until the runout is determined to be increase.27. A method for adjusting the alignment as set forth in claim 25further including the steps of: (e) rotating simultaneously the samestop discs of said input and output adaptor a predetermined degree andrepeating measuring step (a) and comparing step (b), and if the runoutis determined to be lower in the repetition, continue to rotate andrepeat step (a) and (b) until the runout is determined to be increase;and (f) rotating simultaneously the other and the same stop discs ofsaid input and output adaptor a predetermined degree and repeatingmeasuring step (a) and comparing step (b), and if the runout isdetermined to be lower in the repetition, continue to rotate and repeatstep (a) and (b) until the runout is determined to be increase.
 28. Amethod for adjusting the alignment as set forth in claim 26 furtherincluding the step of: maintaining a count of the number of rotations ofthe stop discs and when the count reaches a predetermined number, adjustthe stored acceptable runout limit to a value that is higher but stillwithin an acceptable level.
 29. A method for adjusting the alignment asset forth in claim 26 further including the step of: adjust the degreeof rotation of each of the stop disc depending on the measured level ofrunout.